This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-269266, filed Sep. 22, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a developing agent used in, for example, an electrophotographic apparatus, a method for measuring the free component content of the additive to the developing agent, and a method of evaluating the developing agent.
Various assumptions are made with respect to the filming generation in a developing agent. The presence of free silica that is not attached to the toner is considered to be one of the causes of the filming generation.
For example, where the mixing ratio of silica is unduly large, or where the additive mixing conditions are not appropriate, some of the silica particles are present in a free state separated from the toner particles. As a result, the free silica particles are attached to the carrier particles or attached to and deposited on the inner wall of the developing device, on the developing sleeve, regulating blade, etc. It is then considered that the frictional charging properties of the toner are impaired so as to make it difficult to impart an appropriate charging amount to the toner and so as to promote the filming generation.
The attached state of the additive was analyzed in the past by observation with a scanning electron microscope (SEM), transmitting electron microscope (TEM) or the like. However, these methods are dependent on the visual sensation and the analytical result is not quantitative and, thus, is vague in a large proportion.
An object of the present invention, which has been achieved in view of the situation described above, is to provide a developing agent capable of preventing the occurrence of a drum filming layer.
Another object is to provide a method of quantitatively measuring the content of the free component of the additive to the developing agent.
Further, still another object of the present invention is to provide a method of evaluating the developing agent by quantitatively measuring the content of the free component of the additive to the developing agent.
According to a first aspect of the present invention, there is provided a developing agent, comprising toner particles containing a binder resin and a colorant, the binder resin satisfying the conditions of 2,000xe2x89xa6number average molecular weight Mnxe2x89xa65,000; 8,000xe2x89xa6weight average molecular weight Mwxe2x89xa670,000; and 1.6xe2x89xa6Mw/Mnxe2x89xa635, and an additive mixed with the toner particles, wherein the developing agent satisfies the relationship y less than 0.057x+0.1748, where x represents the total amount of the additive, which is not smaller than 0.2, and y represents the content of the free component of the additive.
According to a second aspect of the present invention, there is provided a method of measuring the free component content of the additive to the developing agent, comprising the steps of forming a pellet by using a developing agent; measuring the front and back surfaces of the pellet by a fluorescence X-ray analytical method, and obtaining the free component content on the basis of the difference in the measured values.
Further, according to a third aspect of the present invention, there is provided a method of evaluating a developing agent, comprising the steps of forming a pellet by using a developing agent; measuring the front and back surfaces of the pellet by a fluorescence X-ray analytical method, obtaining the free component content y on the basis of the difference in the measured values; and examining whether the total addition amount x of the additive and the free component content y meet the relationship y less than 0.057x+0.1748.
According to the present invention, it is possible to measure quantitatively the free component content of the additive mixed with the toner particles of the developing agent.
Also, the present invention makes it possible to evaluate the developing agent by quantitatively measuring the free component content of the additive added to the toner particles of the developing agent so as to select a suitable developing agent that does not generate a drum filming layer.
Further, according to the developing agent of the present invention, it is possible to prevent the drum filming layer from being generated by defining the free component content relative to the addition amount of the additive by using the method described above, making it possible to prevent the off-set occurrence and, thus, to obtain a good image.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.